Colored water immiscible organic liquid

ABSTRACT

Novel disazo colorants or dyes for marking organic liquids, the colorants having the general formula ##STR1## where R 1  is H, CF 3 , or alkyl having from 1 to 4 carbon atoms, 
     R 2  is H, or alkyl having from 1 to 4 carbon atoms, 
     R 3  and R 4  are each H, OCH 3 , OC 2  H 5  or CH 3 , and 
     R 5 , r 6  and R 7  are each H, or alkyl having from 1 to 12 carbon atoms, at least one of said R 5 , R 6  and R 7  being alkyl. 
     The novel compound of the general formula ##STR2## where R 5 , R 6  and R 7  are as described above is provided and is useful as an intermediate in the preparation of said disazo colorants. Methods for the preparation of the colorants are disclosed together with qualitative and quantitative procedures for detecting these colorants in the marked liquids.

This is a division of application Ser. No. 313,591, filed Dec. 8, 1972,now U.S. Pat. No. 3,862,120, patented Jan. 21, 1975.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Colorants or dyes suitable for coloring water immiscible organicliquids, particularly petroleum-derived products, are in general andwidespread commercial use. There exists a particular need for coloringor marking petroleum-derived products and for means to identifypositively the specific colorant or marking ingredient present, and todetermine the concentration thereof.

This need arises primarily through the governmental regulatory action offoreign countries, including certain Provinces of Canada and manyEuropean countries, by which taxes are imposed on motive and heatingfuels. The tax regulations of some countries (and of some States in theUnited States) provide that particular dyes and/or chemical markers mustbe added to taxable or non-taxable fuels, as the case may be, to providea means for identification to prove or disprove the payment of taxes.For example, Manitoba Regulation 51/66 under the Motive Fuel Tax Act ofCanada, provides the following at Paragraph 5 under the caption "Markedand Coloured Motive Fuel":

"Motive fuel used for any of the purposes mentioned in subsection (7) ofSection 3 of the Act shall be given a specific colour and separateidentity by means of a purple dye and a chemical marker, as may bedetermined by the minister."

It is, of course, necessary that the added dye and/or chemical marker becapable of quick and relatively simple identification by non-scientificpersonnel. In other instances, and aside from tax matters, there areoccasions when it is desirable to mark a particular production batch offuel or solvent to prove the origin of the material. These instancesarise in questions of theft and pollution control. As is readilyapparent, any colorant or marker so used must be added in smallconcentration, should not affect the physical or chemical properties ofthe substances to which it is added, and should be easily identified byrelatively quick and simple means.

The tax laws of some countries, for example, certain Provinces inCanada, prescribe that diesel fuel to be sold for use in poweringvehicles on the highway be colorless and bear a higher tax than heatingoils which are required to be colored. This higher tax is an importantfactor in causing the price of diesel fuel to be considerably higherthan that of heating oil. However, diesel fuels and heating oils ofcertain grades have very similar chemical compositions and are virtuallyindistinguishable in their physical properties. In fact, in manyinstances their identification as distinct entities defies ordinarychemical analysis.

The theory of providing particular classes of colored heating oils asopposed to non-colored diesel fuels is that visual inspection will serveto identify the non-taxed heating oil by its color and the highly taxeddiesel fuel by its lack of color. Thus, a dealer in these commoditiesmay have one tank containing colorless, high priced (and taxed) dieselfuel and another tank containing non-taxed, low-priced and coloredheating oil. Unfortunately, this presents opportunities for unscrupulousindividuals to evade lawful taxation. One way is to decolorize thelow-priced, colored heating oil and then sell the colorless product asthe higher priced diesel fuel. Some of the commercially availableadsorbents which serve this purpose are carbon black, charcoal, andvarious clays, silicas and aluminas.

In those countries where the tax laws provide that a highly taxed motivefuel be dyed a specific color, as for example in Great Britain, anotherform of deception is to dilute the taxed, colored fuel with a colorless,non-taxed fuel of virtually the same composition.

Obviously, what is needed is a colorant or series of colorants which arenot removed from petroleum products by the common adsorbents and whichcolorants may be easily identified and quantitatively determined tothwart the tax dodgers and prevent large-scale tax evasions.

DESCRIPTION OF THE PRIOR ART

The term "petroleum products" as used herein refers to suchpetroleum-derived products as gasoline, diesel oils, motive oils,heating or fuel oils, lubricating oils, kerosenes, jet fuels, andnaphthas.

A variety of dyes or colorants is available for coloring petroleumproducts. Among the dyes currently or recently used are those sold underthe trademarks Solvent Reds No. 19,23,24,25,26 and 27, Solvent Blue No.36, Solvent Yellows No. 14 and No. 56, Calco Red Y, Automate Red B,DuPont Oil Red, Automate Yellow -8, DuPont Oil Orange, BASF Liquid RedP-36, BASF Liquid Red SG 7834, BASF Liquid Yellow, BASF Liquid Blue,Automate Blue No. 8, and Automate Orange R. However, these commerciallyavailable dyes suffer from the following disadvantages:

1. They are easily removed from petroleum products to which they areadded by the common adsorbents such as clays, charcoal, carbon black andsilica.

2. In the instance of diesel fuels which contain a variety of naturallyoccurring impurities including dispersed carbon black, unstable red,brown, and yellow color bodies, and fluorescent compounds, many of thecurrent dyes simply disappear and cannot be recognized except at highconcentrations.

3. Convenient "on-the-spot" qualitative tests for the identification ofthese dyes either do not exist or are relatively complex and timeconsuming.

4. Quantitative tests for determing the concentration of these dyes inthe various petroleum products to which they are added either do notexist or are relatively protracted and cumbersome operations.

5. Some dyes, such as Solvent Red No. 23 and Solvent Red No. 24 impartyellowish tints making them rather ineffective for coloring yellowish tobrown-colored diesel oil.

It would therefore be desirable to provide novel colorants for waterimmiscible organic liquids, particularly petroleum products, whichcolorants are highly resistant to removal by the common adsorbents andwhich colorants may be detected qualitatively by on-the-spot testing andwhich may be determined quantitatively by convenient laboratory methods.

Generally, it is an object of this invention to improve on the art ofmarking water immiscible organic liquids with a colorant and ofidentifying said colorant. More specifically, it is an object of thepresent invention to improve on the art of marking petroleum productswith a colorant and identifying said colorant rapidly and efficiently inthe presence of pre-existing natural coloring bodies and/or added dyes.

It is another object of this invention to provide novel colorants ordyes which are soluble in water immiscible organic liquids and arehighly resistant to removal from solution therefrom by the adsorbentswhich are commonly used for extracting the present solvent dyes and/ornatural coloring bodies.

Another object of the present invention is to provide a novelintermediate for the preparation of the novel colorants of thisinvention.

It is another object of this invention to provide a simple "on-the-spot"qualitative test for the rapid identification of said novel colorants.

It is a further object of the present invention to provide an efficientand relatively simple laboratory method for the identification of thenovel colorants of this invention.

Another object of this invention is to provide an efficient laboratorymethod for the quantitative determination of the disazo colorants ofthis invention.

A still further object of this invention is to provide colored waterimmiscible organic liquids containing the novel colorants of the presentinvention, which colorants are highly resistant to removal from solutionby the commonly used adsorbents.

The fulfillment of these and other related objects of this invention maybe more readily appreciated by reference to the following specification,examples and appended claims.

SUMMARY OF THE INVENTION

The present invention provides novel disazo colorants or dyes forcoloring water immiscible organic liquids, which colorants are highlyresistant to removal from said organic liquids, said colorants havingthe general formula ##STR3## where R₁ is H, CF₃, or alkyl having from 1to 4 carbon atoms,

R₂ is H or alkyl having from 1 to 4 carbon atoms,

R₃ and R₄ are each H, OCH₃, OC₂ H₅ or CH₃, and

R₅, r₆ and R₇ are each H or alkyl having from 1 to 12 carbon atoms, atleast one of said R₅, R₆ and R₇ being alkyl.

One of the preferred disazo colorants of this invention is where R₁ isCF₃, R₂ is H, R₃ is OCH₃, R₄ is CH₃, R₅ is C₇ H₁₅, R₆ is C₁₂ H₂₅ and R₇is H, according to the formula ##STR4## said colorant hereinafter beingreferred to as Colorant (I).

Another of the preferred disazo colorants comprises a mixture ofcompounds having the formula ##STR5## where R₁, R₂, R₃ and R₄ are each Hor CH₃, said colorant hereinafter being referred to as Colorant (II).

Colorants (I) and (II) are conveniently provided as low viscosityliquids containing xylene.

The present invention also provides a novel intermediate for preparingthe present disazo colorants, said intermediate having the generalformula ##STR6## where R₅, R₆ and R₇ are each H or alkyl having from 1to 12 carbon atoms, at least one of said R₅, R₆ and R₇ being alkyl.

The terms colorants, dyes and markers are used interchangeably herein.

In general, the disazo colorants of this invention may be prepared by aprocess which comprises (1) diazotizing a compound of the formula##STR7## where R₁ is H, CF₃ or alkyl having from 1 to 4 carbon atoms andR₂ is H or alkyl having from 1 to 4 carbon atoms, (2) coupling saiddiazotized compound with a compound of the formula ##STR8## where R₃ andR₄ are each H, OCH₃, OC₂ H₅ or CH₃, to form an aminoazo product, (3)diazotizing the aminoazo product so formed, and (4) coupling saiddiazotized aminoazo product with a compound of the formula ##STR9##where R₅, R₆ and R₇ are each H or alkyl having from 1 to 12 carbonatoms, at least one of said R₅, R₆ and R₇ being alkyl.

As described in more detail in the following Examples, in the instanceof the preparation of Colorant (I), m-aminobenzotrifluoride isdiazotized and coupled to p-cresidine. The resultant aminoazo product isdiazotized, and the diazotized product thereof is coupled to2-(dodecylphenylamino) heptylnaphthalene to provide the product havingthe formula ##STR10## The intermediate of this invention, ##STR11##where R₅, R₆ and R₇ are each H or alkyl having from 1 to 12 carbonatoms, at least one of said R₅, R₆ and R₇ being alkyl, is prepared by aprocess which comprises condensing at a temperature of from about 185°to about 230° C. and in the presence of xylene, iodine and hydrochloricacid, a beta naphthol of the formula ##STR12## where R₅ is H or alkylhaving from 1 to 12 carbon atoms with a substituted aniline of theformula ##STR13## where R₆ and R₇ are each H or alkyl having from 1 to12 carbon atoms, at least one of said R₅, R₆ and R₇ being alkyl, andcooling and washing the reacted mass to provide the desired product.

One of the preferred intermediates of this invention is where R₅ is C₇H₁₅, R₆ is C₁₂ H₂₅ and R₇ is H.

The novel colorants of this invention display a surprisingly highsolubility in virtually all water immiscible organic liquids such asparaffinic hydrocarbons, aromatic hydrocarbons, alkyl-aryl hydrocarbonssuch as alkyl benzenes and alkyl naphthalenes, petroleum products suchas gasoline, kerosene, naphthas, diesel fuels, jet fuels, heating fuels,and lubricating oils, chlorinated solvents such as chloroform, ethylenedichloride, chlorobenzenes and perchloroethylene, alcohols, esters,ketones, and glycol ethers. This is in contrast to the currentlyavailable dyes which have relatively low solubilities in most waterimmiscilbe organic liquids, particularly in petroleum products such asgasoline, diesel fuels and heating oils. For example, a solubility inthese products of 5% is considered extremely high, while most dyes havesolubilities considerably lower than 2%. Colorants (I) and (II) hereofare significantly more soluble in aromatic and hydrocarbon solvents thanare the current dyes now in use for coloring petroleum products. Infact, these two Colorants are soluble in all proportions in isooctane,gasoline and diesel oil. It is well known that isooctane is a very poorsolvent for the conventional dyes.

A concentration of 20 parts per million of Colorant (II) was chosen tobe added to a petroleum product to achieve a 100% marked, i.e., a fullymarked product. This is on the basis that such concentration provides acolor intensity comparable to that used by the various governmentsprescribing the use of dyes for coloring fuels for tax purposes. Due tothe fact that the color intensity of Colorant (I) is slightly less thanthat of Colorant (II), a concentration of 23 parts per million ofColorant (I) in a petroleum product provides a 100% marked (or colored)product. A petroleum product found to contain only 2 parts per millionof Colorant (II) would therefore be a 10% marked product and wouldindicate that one part of the originally 100% marked product had beendiluted with 9 parts of a non-marked but similar petroleum product.

Another and perhaps most important attribute of the present disazocolorants is their relative chemical inertness and resistance toadsorption from petroleum products in which they are dissolved. Thisattribute makes it possible by means of the common adsorbents toseparate out other conventional dyes and/or naturally occurring colorbodies, leaving the disazo colorants of this invention in solution wherethey may be identified and their concentration determinedquantitatively. Qualitative identification by a rapid on-the-spotprocedure enables tax officials to determine quickly the existence ofthe added disazo colorant and therefore the likelihood of tax evasion. Aquantitative determination of the concentration of disazo colorant in asuspected petroleum product provides proof of the degree of dilution byprohibited diluents.

A visual on-the-spot field test for the presence in a petroleum productof one of the disazo colorants of this invention is provided by thefollowing procedure:

A convenient sample of the colored fuel (50 to 100 ml.) is shakenvigorously with 1 or 2 grams of an adsorbent such as a clay, orpreferably a hydrated silica commercially available under the trademarkHI-SIL No. 233. The mixture is allowed to settle to form a clear upperlayer and a sediment, whereupon the color of the clear fuel becomesvisible while the conventional added dyes or color bodies naturallypresent in the fuel are removed by the adsorbent. The characteristiccolor of the disazo colorant is evident in the clear layer.

By this simple qualitative test, it is possible to detect the color ofthe disazo colorant even where the 100% marked fuel has been diluted toa 5% marked product. In the instance where the petroleum product isgasoline, the same procedure is followed except that the adsorbent ispreferably silica gel.

To determine the quantity of disazo colorant present in the marked fuel,the same procedure as for the qualitative test is followed except thatthe clear layer is separated from the sediment by filtration. Theabsorbance of the filtrate is measured spectrophotometrically at a wavelength which depends upon the specific colorant used. Thus, for example,a wave length of 550 mμ is used if the colorant is Colorant (II), or580-590 mμif the colorant is Colorant (I). The absorbance obtained fromthe marked sample is compared with the previously determined absorbancesat various concentrations of the particular colorant in question. It hasbeen determined, as set forth in the Examples hereinafter described,that a straight line graph is obtained when the absorbances of Colorants(I) and (II) are each plotted against their respective concentrations.

An alternate quantitative procedure for the determination of thequantity of disazo colorant present in gasoline comprises percolating ameasured sample of the colored gasoline through a column of highlyactivated alumina to deposit all color bodies present thereon. Thecolumn is then washed with isooctane which removes any residualgasoline, followed by toluene which preferentially dissolves thecolorants of the present invention leaving the conventional dyes andnaturally occurring color bodies on the column. The absorbance of thetoluene solution is measured and compared, as before, with thepreviously determined absorbances of the colorant in question todetermine the concentration of disazo colorant.

A more detailed laboratory identification test for the presence ingasoline of the disazo dyes of the present invention is provided by theuse of Thin Layer Chromatography (TLC). A portion of the toluenesolution of the colorant obtained by passage of the colored gasolinethrough a column of activated alumina is concentrated and spotted on astandard Merck Silica Gel coated glass plate along with a standard spotof the particular colorant in question. The color and R_(f) valuesobtained for the test specimen are compared with that of the standardknown Colorant to establish the identity of the colorant in thegasoline. It was established by using standard Merck Silica Gel coatedglass plates and toluene as the eluent that the R_(f) values forColorant (I) are 0.88 at 10 cm. and 0.83 at 17 cm., and those forColorant (II) are 0.86 at 10 cm. and 0.81 at 17 cm. These values aremuch higher than those for the conventional petroleum product dyes whichgenerally range from about a low of 0.22 to a high of 0.74 with mostvalues lying in the range of from 0.22 to about 0.59. The unusually highR_(f) values for the present disazo colorants serve as another means forpositive identification of these dyes.

Thin Layer Chromatography may also be employed on the benzene solutionof colorant removed from colored diesel fuel by means of a highlyacid-activated clay known commercially as Impact No. 150. It isreiterated that the present disazo colorants are highly resistant toremoval from solution by the ordinary adsorbents in common use. However,an unusually active acid-activated clay such as Impact No. 150, or ahighly activated alumina will remove even the disazo colorants of thisinvention from solution.

The invention will now be illustrated by a number of examples, it beingunderstood, however, that these examples are given by way ofillustration and not by way of limitation, and that many changes andalterations may be effected in quantity, choice of raw material andprocess conditions in general without affecting in any way the scope andspirit of the invention as recited in the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1 Preparation of theDisazo Colorant ##STR14##

A slurry was formed containing 0.20 gram mol of m-aminobenzotrifluoridein 300 ml. water containing a dispersing agent known commercially asSotex N. To this slurry 0.50 mol of HCl was added slowly with stirringto form the amine hydrochloride and to give a fine dispersion thereof.The amine hydrochloride was diazotized with the approximatelytheoretical quantity of sodium nitrite required, at a temperature ofabout 0° C. in the presence of about 300 g. of ice to yield a turbidbrownish solution. A solution was prepared containing 0.20 gram mol ofp-cresidine in 200 ml. water, 0.22 mol HCl and 4 drops of Sotex N. Icewas added to this solution to maintain it at about 0° C. To thissolution, the diazotized amine was quickly added with maximum stirringto effect coupling thereof with the p-cresidine.

The coupled product was diazotized by raising the temperature thereof toabout 15° C. and adding 0.20 mol of sodium nitrite thereto in smallportions. The temperature of this diazotized product was then cooled toabout 10° C. after which 0.2 mol of the reactant 2-(dodecylphenylamino)heptylnaphthalene was added to effect coupling therewith and provide thefinal product in the reaction mixture. The reaction mixture was warmedand water separated therefrom to provide the final product.

EXAMPLE 2 Preparation of the Disazo Colorant comprising a mixture ofcompounds having the general formula: ##STR15## where R₁, R₂, R₃ and R₄are each H or CH₃.

A mixture of aniline, toluidine and mixed xylidines was partiallydiazotized in the presence of insufficient aqueous HCl with the resultthat the diazo compounds formed coupled with the excess aniline,toluidine and mixed xylidene to form mixed amino azo compounds. Themixed amino azo compounds were diazotized in the usual fashion. Thisdiazotized mixture was added to a solution containing the couplingcomponent 2-(dodecylphenylamino) heptylnaphthalene in a molar quantitysubstantially equal to the number of moles of mixed amino azo compoundsemployed to form the desired product.

EXAMPLES 3 - 7

The procedure of Example 2 was repeated except that the final couplingcomponent was varied as indicated in the following table to yield theindicated disazo colorant:

                                      Table 1                                     __________________________________________________________________________                       In each of the following dyes, R.sub.1, R.sub.2,                              R.sub.3 and R.sub.4 are each H or CH.sub.3.                Ex. Coupling Component                                                                           Disazo Colorant                                            __________________________________________________________________________    3   2-(dodecylphenylamino)- naphthalene                                                           ##STR16##                                                 4   2-(phenylamino) heptylnaphthalene                                                             ##STR17##                                                 5   2-(butylphenylamino) heptylnaphthalene                                                        ##STR18##                                                 6   2-(dimethylphenylamino)                                                                       ##STR19##                                                 7   2-(phenylamino) dodecylnaphthalene                                                            ##STR20##                                                 __________________________________________________________________________

Detection of Disazo Colorants in Petroleum Products

EXAMPLE 8 Detection of Disazo Colorant in Diesel Heating Oil

Twenty-three parts per million of a disazo colorant having the formula##STR21## were added to a diesel heating fuel having a naturalyellow-brownish color to provide a fully marked (100%) deeply coloredsolution. One hundred milliliters of the colored fuel were shakenvigorously with 1 gram of a hydrated silica commercially available underthe trademark Hi-Sil No. 233. The mixture was allowed to settle to forma clear upper layer of fuel and a lower sediment layer. The clear fueldisplayed the characteristic bluish color of the disazo colorant. Theclear colored fuel may be decanted into a test tube to a depth of 4-5inches and the upper surface (meniscus) viewed by transmitted orreflected light, or the total depth may be viewed axially to detect thecharacteristic tint of the added colorant. In this manner, as little as5% of marked fuel diluted with 95% of unmarked fuel (equivalent to acolorant concentration of about 1 ppm) may be detected.

The above procedure was repeated except that the disazo colorantemployed was a mixture of compounds embraced by the formula: ##STR22##where R₁, R₂, R₃, and R₄ are each H or CH₃, and the concentration ofsaid colorant in the fuel was 20 parts per million. The characteristicreddish tint of this colorant was detected in the clear fuel layer.

This example demonstrate the removal of naturally-occurring color bodiesby a common adsorbent and resistance of the present disazo colorants toadsorption by said adsorbent.

EXAMPLE 9 Detection of Disazo Colorant in Gasoline

Colorant (I) was added to gasoline at a concentration of 23 parts permillion (100% marked fuel) to provide a tinted fuel. It is understoodthat the gasoline may have a purple color if red colored gasoline wasused, or a dark murky color if the gasoline was colored with theconventional orange and yellow dyes. One hundred milliliters of thetinted fuel were shaken vigorously with 20 grams of silica gel. Themixture was allowed to settle to form a clear upper layer and a lowersediment layer. The clear layer displayed the characteristic blue colorof Colorant (I).

The above procedure was repeated except that Colorant (II) was employed.The characteristic bluish-red tint of Colorant (II) was observed in theclear fuel layer.

EXAMPLE 10 Quantitative Determination of Disazo Colorant in No. 2 DieselHeating Oil

Colorant (I) was added at a concentration of twenty-three parts permillion to a dark No. 2 diesel-heating fuel to provide a fully marked(100%) fuel. Fifty milliliters of the marked fuel were shaken with 2.5grams of Hi-Sil No. 233 and allowed to settle. The tinted fuel wasseparated by filtration and its absorbance was measuredspectrophotometrically at a wave length of 580 mμ.

The above procedure was repeated except that the followingconcentrations of Colorant (I) were employed:

    ______________________________________                                                PPM     % Marked Fuel                                                 ______________________________________                                                11.5    50                                                                    2.3     10                                                                    1.1     5                                                                     0       0                                                             ______________________________________                                    

The above procedure was repeated on 9 additional No. 2 diesel heatingoils containing the same concentrations of Colorant (I) to give a totalof 10 different sets of absorbance values. The averages of theabsorbances for each concentration were determined and are set forth inthe following table (Table 2).

                  TABLE 2                                                         ______________________________________                                        PPM      % Marked Fuel  Observed Absorbance                                   ______________________________________                                        23       100            0.373                                                 11.5     50             0.190                                                 2.3      10             0.045                                                 1.1      5              0.026                                                 0        0              0.007                                                 ______________________________________                                    

Colorant (II) was carried through the same procedure as that forColorant (I) employing the following concentrations.

    ______________________________________                                                PPM     % Marked Fuel                                                 ______________________________________                                                20      100                                                                   10      50                                                                    2       10                                                                    1       5                                                             ______________________________________                                    

The absorbances were determined at a wave length of 550 mμ, and werefound to be the same as for Colorant (I).

The foregoing values are depicted graphically in FIG. 1 in which theobserved absorbance is plotted along the ordinate and the percent markedfuel (parts per million of disazo colorant) is plotted along theabscissa.

By reference to the graph of FIG. 1, it is possible for an analyst tomeasure the absorbance of an unknown diesel fuel according to theprocedure set forth in this Example and determine the quantity (partsper million) of disazo colorant present in the unknown fuel. Thus, forexample, if it were determined that 11.5 parts per million of Colorant(I) were present in the fuel, it would follow that the fuel had beendiluted with an equal volume of unmarked (non-colored) fuel with theresult that the fuel is now only 50% marked, or 50% diluted.

The foregoing demonstrates that the method of this Example provides anefficient, rapid and accurate method for identifying and quantitativelydetermining the disazo colorants present in petroleum products evenwhere such products contain other naturally occurring or added colorbodies.

EXAMPLE 11

The procedure of Example 10 was repeated except that seven different No.1 diesel oils were used. The individual absorbances were averaged andare set forth in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    PPM                                                                           Colorant (I)                                                                          Colorant (II)                                                                          % Marked Fuel                                                                          Observed Absorbance                                 __________________________________________________________________________    23      20       100      0.348                                               11.5    10       50       0.178                                               2.3     2        10       0.034                                               1.1     1        5        0.019                                               0       0        0        0                                                   __________________________________________________________________________

These values are depicted graphically in FIG. 2 in which the observedabsorbances are plotted along the ordinate and the percent marked fuel(parts per million of disazo colorant) is plotted along the abscissa.

For comparative purposes, the same No. 1 diesel oil was colored with thedye (Solvent Red No. 24) currently in use in France and the UnitedKingdom (and proposed in Germany) for tinting petroleum fuels inconcentrations as prescribed by the laws of these countries and carriedthrough the same procedure as set forth in Example 10. Solvent Red No.23 is currently in use in Italy. These concentrations for a 100% markedfuel are 10 ppm for France, 5 ppm proposed for Germany, 4 ppm for theUnited Kingdom and 30 ppm for Italy. In addition, a 10% marked fuel wasprepared for each diesel fuel. The absorbances for each of thesesolutions were compared with those set forth in the graph in FIG. 2 todetermine the dye content of the respective solutions remaining aftertreatment with the Hi-Sil No. 233 decolorizing agent. The results wereas follows:

    ______________________________________                                                  % Dye Remaining                                                               100% Marked Fuel                                                                          10% Marked Fuel                                         ______________________________________                                        France      54            5                                                   Germany     34            2                                                   United Kingdom                                                                            19            1                                                   Italy       37.8          4.4                                                 ______________________________________                                    

This illustrates that the current dyes used in the indicated countriesare fairly easily removed by an adsorbent which has little or no effecton the present disazo colorants.

EXAMPLE 12 Quantitative Determination of Disazo Colorant in Gasoline

Twenty-three parts per million of Colorant (I) were added to gasoline toprovide a fully marked (100%) product. Fifty milliliters of the markedgasoline were diluted with an equal volume of isooctane (hexane is alsosuitable) and percolated through a 10 gram column of activated alumina.An excellent chromatographic column for this purpose is 25 × 10.5 mmwith integral 200 ml reservoir, and lower Teflon plug stopcock. A freshhighly active chromatographic grade of alumina is required, at least theequal of that commercially available under the trademark Alcoa F-20(80 - 200 mesh). The principal problem here is to ensure completeretention of marker dye on the column. Other gasoline dyes and additivesare strongly adsorbed near the very top of the column.

After passage of fuel mixture the marker dye is visible as a blue-blackband or zone, perhaps somewhat diffused, in the upper half of thecolumn. At low marked fuel concentrations the marker may be poorlyvisible, or obscured by other colorants, and is not necessarily confinedtotally to the visible area.

The column was then given an isooctane wash to dislodge adheringgasoline, and thereafter toluene was passed therethrough. The marker dyewas observed to concentrate sharply at the toluene front and move downthe column. Collection of eluent in a 25 ml. volumetric was begunshortly before dye arrived at the bottom and continued well past thepoint at which no more color is visible. Almost all marker was collectedin approximately 10 ml. eluent, but up to 25 ml. may be collected toensure no loss.

The collected eluent was diluted to 25 ml. and the absorbance wasmeasured at a wave length of 586 mμ. Absorbance of toluene is zero atthese wave lengths, and impurities or other gasoline dyes are retainedon the column. Therefore the absorbance reading can be directly relatedto marker dye concentration, allowing for the proportion of initialsample volume to 25 ml. eluent.

The above procedure was repeated with the following concentrations ofColorant (I) present in the gasoline:

    ______________________________________                                        PPM             % Marked Gasoline                                             ______________________________________                                        11.5            50                                                             2.3            10                                                             0 (Blank)       0                                                            ______________________________________                                    

In addition, 4 more samples of gasoline colored in the same manner andat the same concentrations were carried through this procedure to give atotal of 5 different sets of absorbances. The average of the absorbancesfor each concentration were determined and are set forth in Table 4.

                  Table 4                                                         ______________________________________                                        PPM     % Marked Gasoline                                                                             Observed Absorbance                                   ______________________________________                                        23      100             0.722                                                 11.5    50              0.362                                                 2.3     10              0.075                                                 0       0               0                                                     ______________________________________                                    

These values are depicted graphically in FIG. 3 in which the observedabsorbances are plotted along the ordinate and the percent marked fuel(parts per million of Colorant I) is plotted along the abscissa.

Comparing the absorbances plotted in FIG. 3 with known standardsolutions of Colorant (I) at 100 and 10% marked fuel levels, it wasfound that there was only a 4% color loss at the 100% marked fuel leveland no apparent loss at the 10% level.

EXAMPLE 13 Identification of Disazo Colorant - Thin LayerChromatographic Procedure Diesel Heating Oil

Diesel heating fuel was marked with 23 parts per million of Colorant(I). One-hundred milliliters of the marked fuel were shaken thoroughlywith 6 grams of an acid activated bentonite clay commercially availableunder the trademark Impact No. 150 until the fuel was decolorized. Theclay was filtered, washed free of oil with isooctane, and sucked fairlydry. It is not advisable to suck more than minimum air through the cakebecause the color value of adsorbed impurities will substantiallyincrease in the presence of air and the low pH clay. Colorant (I) andsome impurities were then removed from the clay by a careful wash withbenzene (about 5 - 10 ml), and the eluent concentrated by steam bath orhot plate, either down to an appropriate concentration or nearly todryness and redissolved in 1-2 ml benzene. The choice of concentrationwill be dictated by the amount of color visible in the initial eluentwhich may be considerable or virtually invisible in the presence ofaccompanying impurities.

One to five microliters of the benzene solution were spotted on astandard Merck Silica Gel coated glass plate, along with a standard spotof Colorant (I), and the chromatogram was developed with toluene. Thecolor of both spots was found to be a characteristic blue-black shade.

The R_(f) values of Colorant (I) from said diesel heating fuel weredetermined at 10 and 17 centimeters respectively and were found to be0.88 and 0.83 respectively, which is in close agreement with those of astandard spot of Colorant (I).

In view of the many sensitive variables associated with R_(f) values inthe thin layer chromatography technique, it is always advisable to runan accompanying standard spot rather than to rely on a fixed R_(f) valuefor any particular dye. However, the following table (Table 5) indicatesR_(f) values obtained for typical dyes which are in current use forcoloring gasoline and might be present in any particular brand ofgasoline. These are relative rather than absolute values.

The R_(f) values were obtained by spotting 1 microliter of 50 mg dye/10ml. of a xylene solution on Merck plates, 1 cm above the bottom. Valueswere determined for 10 and 17 cm solvent front travel with the former(approximately 20 minutes development time) giving the best distinction.

                  TABLE 5                                                         ______________________________________                                               DYE          10 cm     17 cm                                           ______________________________________                                        Colorant (I)        0.88      0.83                                            Colorant (II)       0.86      0.81                                            Commercial Designation                                                        Red TAX             0.27      0.34                                            Calco Red Y         0.40      0.46                                            Orange TX           0.30      0.39                                            Automate Red B      0.38      0.39                                            DuPont Oil Red      0.33      0.32                                            Automate Yellow No. 8                                                                             0.74      0.73                                            Red AB4             0.28      0.32                                            Purple A            0.39      0.35                                            Automate Orange R   0.47      0.42                                            Automate Blue No. 8 0.33      0.30                                            Orange 27           0.59      0.54                                            DuPont Oil Orange   0.31      0.29                                            Solvent Yellow No. 56                                                                             0.43      0.39                                            Solvent Blue No. 36 0.10      0.09                                            BASF Liquid Red P-36                                                                              0.63                                                      BASF Liquid Red SF7834                                                                            0.22                                                      BASF Liquid Yellow  0.59                                                      BASF Liquid Blue    0.33                                                      ______________________________________                                    

It is observed that only the dye known as Automate Yellow No. 8 has anR_(f) value which approaches that of the present disazo colorants.However, the color shade of Automate Yellow No. 8 is markedly differentfrom that of the present disazo colorants, and therefore completelydistinguishable on that basis alone.

EXAMPLE 14 Identification of Disazo Colorant - Thin Layer ChromatographyGasoline

Colorant (I) was added to gasoline and was separated by the sameprocedure as described in Example 12, i.e., by a column of activatedalumina. A portion of the toluene solution of Colorant (I) dissolvedfrom the alumina was subjected to the same TLC procedure as described inExample 13 to yield the same characteristic blue-black spot and the sameR_(f) value as before.

EXAMPLE 15 Preparation of 2-(dodecylphenylamino) heptylnaphthalene

The following are charged to a 1 liter flask equipped with stirrer,reflux condenser and water trap:

    ______________________________________                                               p-dodecylaniline                                                                           1.0 mol.                                                         heptyl beta naphthol                                                                       1.1 mol.                                                         xylene       60 g.                                                            iodine       2 g.                                                             HCl (32% Be) 5 g.                                                      ______________________________________                                    

The mixture is heated as rapidly as possible to reflux temperature. Freewater from the HCl is evolved gradually up to 205° C. where refluxingbegins. The reaction proceeds at a temperature of about 214° C. and thenslowly rises to 225°-230° C. to completion of the reaction. Thecompletion of the reaction is signified by the cessation of waterevolution, or its reduction to a preselected arbitrary low level. Themass is then cooled to about 105° C. and washed with a 45% KOH solution,washed until neutral and then dried.

What is claimed is:
 1. A colored water immiscible organic liquid havingdissolved therein a disazo colorant corresponding to the formula##STR23## in which R₁ is H, CF₃, or alkyl having from 1 to 4 carbonatoms, R₂ is H or alkyl having from 1 to 4 carbon atoms, R₃ and R₄ areeach H, OCH₃, OC₂ H₅ or CH₃ and R₅, R₆ and R₇ are each H or alkyl having1 to 12 carbon atoms, at least one of said R₅, R₆ and R₇ being alkyl,said disazo colorant being highly resistant to removal from said organicliquid by the commonly used adsorbents such as carbon black, charcoal,clay and silica.
 2. The colored water immiscible organic liquid of Claim1 wherein R₁ is CF₃, R₂ is H, R₃ is OCH₃, R₄ is CH₃, R₅ is C₇ H₁₅, R₆ isC₁₂ H₂₅, and R₇ is H.
 3. A colored water immiscible organic liquidhaving dissolved therein a disazo colorant comprising a mixture ofcompounds having the formula ##STR24## where R₁, R₂, R₃ and R₄ are eachH or CH₃, said disazo colorant being highly resistant to removal fromsaid organic liquid by the commonly used adsorbents such as carbonblack, charcoal, clay and silica.